C Programming - C Logical Operators

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C Programming - C Logical Operators

C Logical Operators

Logical operators in C are used to perform logical operations, typically in decision-making and control flow statements. They evaluate expressions and return a boolean result: 1 (true) or 0 (false). Logical operators often work in conjunction with relational operators to build complex conditions.

List of Logical Operators

Key Characteristics

1. Logical AND (&&):
• Evaluates to true (1) only if both operands are true.

int a = 10, b = 20;
if (a > 5 && b < 30) {
    printf("Condition is True\n");
} else {
    printf("Condition is False\n");
}
// Output: Condition is True

1. Logical OR (||):
• Evaluates to true (1) if at least one operand is true.

int a = 10, b = 20;
if (a > 5 || b > 50) {
    printf("Condition is True\n");
} else {
    printf("Condition is False\n");
}
// Output: Condition is True

1. Logical NOT (!):
• Reverses the logical state of its operand.
• If the condition is true, ! makes it false, and vice versa.

int a = 10;
if (!(a > 5)) {
    printf("Condition is False\n");
} else {
    printf("Condition is True\n");
}
// Output: Condition is True

Truth Tables

Logical AND (&&):

Logical OR (||):

Logical NOT (!):

Example Program

#include <stdio.h>
 
int main() {
    int a = 10, b = 5, c = 0;
 
    // Logical AND
    if (a > b && b > c) {
        printf("Both conditions are true.\n");
    }
 
    // Logical OR
    if (a > b || c > b) {
        printf("At least one condition is true.\n");
    }
 
    // Logical NOT
    if (!c) {
        printf("c is zero (false).\n");
    }
 
    return 0;
}

Output:

Both conditions are true.
At least one condition is true.
c is zero (false).

Short-Circuit Evaluation

• AND (&&): If the first operand is false, the second operand is not evaluated because the result is already determined to be false.
• OR (||): If the first operand is true, the second operand is not evaluated because the result is already determined to be true.

Example:

int a = 5, b = 0;

if (a > 10 && b++) {
    // b++ is not executed because a > 10 is false.
}

printf("b = %d\n", b); // Output: b = 0

Operator Precedence

Example:

int a = 5, b = 10, c = 15;
if (a < b || b > c && c > a) {
    // Evaluates as: b > c && c > a (true), then a < b || true (true)
    printf("True\n");
}

Applications

1. Decision Making:
• Combining multiple conditions in if statements.

if (age > 18 && age < 60) {
    printf("Eligible\n");
}

1. Loops:
• Controlling loop execution with complex conditions.

while (x > 0 && y < 100) {
    // Perform operations
}

1. Validations:
• Checking multiple constraints for input validation.

if (score >= 0 && score <= 100) {
    printf("Valid score.\n");
}

Logical operators are essential for writing efficient and readable conditional expressions in programming. They provide flexibility in evaluating complex scenarios with minimal code.